(A) Field of the Application
The present application relates to a sigma-delta modulator (SDM) and the quantizer thereof, and a quantization method for the sigma-delta modulator.
(B) Description of the Related Art
There are many types of analog-to-digital converters (ADC), such as flash ADCs, pipelined ADCs, successive approximation (SA) ADCs and sigma-delta modulators (SDM). These are all commonly used ADCs and each of them is suitable for certain applications.
Because the power consumption of a flash ADC is proportional to the square of the resolution, the power consumption is increased when the resolution of a flash ADC increases. In general, the increase of the resolution will increase the number of the comparators and the power consumption. The increase of the number of comparators causes an increase in the complexity of circuit design and cost.
The resolution (N) and oversampling ratio (OSR) for a known trace type flash ADC have to comply with the equation:
            2      N        <                  2        π            ⁢      OSR        ,and the flash ADC needs a specific start-up circuit to avoid an unstable sigma-delta modulator.